M-reps A New Object Representation for Graphics外文文献.pdfVIP

February 8, 2000 Submitted to ACM TOG M-Reps: A New Object Representation for Graphics Stephen M. Pizer, Andrew L. Thall, David T. Chen Department of Computer Science University of North Carolina, Chapel Hill Abstract M-reps are a multiscale approach to the modeling and rendering of 3D solid geometry. Traditional geometric models, whether b-reps or CSG, are represented at infinitesimal spatial scale and then require simplification to meet needs requiring coarser scale or smaller data sets. We have developed a model that is designed at successively smaller scales and supports a coarse-to-fine hierarchy in design, rendering, physical deformation, and other graphics operations. We base our representation onfigural models , defined at coarse scale by a hierarchy of figures – protrusions, indentations, corners, neighboring figures, and included figures – which simultaneously represent solid regions and their boundaries. To capture local shape at scale and thus local zoom-invariance, the figural components imply a fuzzy, i.e., probabilistically described boundary position with a width- and scale-proportional tolerance. At small scale these figures are made precise by displacement maps, geometric textures, or image textures. While these models can exist in 2D, we focus on models of 3D objects. We note the needs of a variety of graphics operations and thus motivate the following definition of an m-rep. A model for a single figure is made from a mesh of medial atoms (hence the name m-reps), each atom describing not only a position and width, but also a local figural frame implying figural directions, and an object angle between opposing, corresponding positions on the implied boundary. In addition, wid